The current state-of-the-art for video encoding is the ITU-T H.264/AVC video coding standard. It defines a number of different profiles for different applications, including the Main profile, Baseline profile and others.
There are a number of standards for encoding/decoding images and videos, including H.264/AVC, that use block-based coding processes. In these processes, the image or frame is divided into blocks, typically 4×4 or 8×8 in pixels, and the blocks are spectrally transformed into coefficients, quantized, and entropy encoded. In many cases, the data being transformed is not the actual pixel data, but is residual data following a prediction operation. Predictions can be intra-frame, i.e. block-to-block within the frame/image, or inter-frame, i.e. between frames (also called motion prediction).
The motion estimation process involved in inter-frame encoding relies upon a rate-distortion expression that only accounts for some aspects of the actual distortion and coding rate. In particular, it ignores distortion due to quantization of the residual values and the coding rate attributable to the quantized transformed residual values (the quantized transform domain coefficients). However, it would be computationally impractical for an encoder to determine these quantities for every candidate motion vector under evaluation during the encoding process in order to incorporate these quantities into the rate-distortion analysis.
It would be advantageous to provide for an encoder and methods or processes for encoding that improve rate-distortion performance.
Similar reference numerals may have been used in different figures to denote similar components.